The difficulty to take good, clear, and interesting picture of birds is not new. Good rightly photographically focused of bird specimens is challenging by the nervous and fast nature of them. Unpredictability is another one among others such as strong exposure variation (From deep shadow to brightly sunny areas). Bird photographer specialists can surely bring you a vast and lengthily presentation about these challenges.
Trying the Fujifilm X-S10 camera model, I was particularly interested to see how the autofocus tracking system can manage the task in taking picture good bird snapshots and, I must admit, it did well even in using it in conjunction of the Fujinon XF55-200mm F3.5-4.8 R LM OIS which is one of my preferred optics (but older) in Fuji X-mount line up. I can imagine that performance will be better with the more recent Fuji X-mounts that have been introduced lately.
A last word regarding bird photography is the preparation it needs in term of knowledge of the bird habits and how to not disturb your main subject even for a snap shooter like me. And, of course, a lot of persistence!